In U.S. Pat. No. 3,869,268, herein incorporated by reference, a method and apparatus for forming chopped glass fiber strand is disclosed. As the glass strand is chopped, it passes along a series of two vibratory conveyors, the first of which vibrates at an amplitude greater than the second. The second vibratory conveyor is a tray which passes under a drying apparatus, such as an infrared dryer, a gas oven, an electric oven and the like. The drying apparatus heats the vibratory conveyor as it dries the glass strand. This drying is important, since all of the glass fibers have been previously coated with a lubricant binder and/or size. The lubricants employed are normally thermoplastic and harden when cooled. The heat along the tray maintains the binder in such a condition that it will not stick to the tray.
In the formation of the tray, reinforcing ribs and connections to the vibrators are located at the bottom of the tray. These ribs are made of steel and are welded directly to the bottom of the tray. Being constructed of metal, these ribs act as heat sinks and tend to draw heat away from the tray at their connections to the tray. With certain binders, such a cooling of the tray at those points resulted in sticking of the chopped glass fiber strand to the tray at these heat sinks, thus clogging the tray and adversely affecting production in such a manner that these binders could not be used in forming chopped glass fiber strand by this method. It is desirable, therefore, to eliminate any such sticking problem so that all binders can successfully be employed on the glass strand produced by the method of U.S. Pat. No. 3,869,268.
In U.S. Pat. Nos. 3,133,628 and 3,191,763 a composite insulated vibratory tray is shown, however, this tray includes spacer elements 27 between the trays which would act as heat sinks and thus be unsatisfactory for use in the present invention.